Originally Posted by bargainguy

One of the problems with the Neos is that the frame was designed around it. You can't just swap in a different rear derailleur should the derailleur start acting up, as the derailleur is mounted just ahead of the rear axle (effectively the driveside chainstay). There's no place to hang a dropout-mounted rear derailleur.

Thor sells a Tern adapter for models that use the Neos, but I don't see any Dahon adapters.

There is a Colorado company called Wheels Manufacturing that makes a Dahon rear derailleur hanger, #27. I've never used one, but it might actually allow your Dahon to use a standard dropout-mounted rear derailleur instead of being locked into the Neos. Please check with them before purchasing, they know more about it than I do:

Wheels Manufacturing Derailleur Hanger 27